High voltage transformer for television receivers

ABSTRACT

An improved high voltage transformer for television receivers and the like. The transformer coils are wound around novel slotted coil form means comprising hollow, electrically insulative means, the interior of which surrounds a portion of the transformer core means and the exterior of which is provided with a plurality of axially spaced circumferential slots. The slots for the high voltage windings are located at progressively increasing radial distances from the core means portion so as to provide a sufficiently great insulative barrier between the coil and the core means to prevent electrical arcing therebetween.

United States Patent [72] Inventors Eug n V011 Fange 880,838 3/1908 Thondarson 336/231X C p 1,062,046 5/1913 Smith 336/231X Julius Kemeny, Suffolk; Sanjar Ghaem- 2,594,915 4/1952 Guillemant.... 336/208X Maggggli, Ch sap ake, Va- 2,799,836 7/1957 Heller et al. 336/198X I211 APPL FOREIGN PATENTS [22] Filed 1969 187 113 2/1967 0 s s R 336/231 [45] Patented Apt 6,1971 [73] Assignee General Electric Company Primary ExaminerThomas J. Kozma N.Y. Attorneys Francis H. Boos, Jr., P rank L. Neuhauser, Oscar B. Waddell, Joseph B. F orman and James E. Espe [54] HIGH VOLTAGE TRANSFORMER FOR TELEVISION RECEIVERS 7 Claims 3 Drawing Figs ABSTRACT: An improved high voltage transformer for televlslon receivers and the like. The transformer coils are U.S. wound around novel slotted coil form means comprising ho]- 336/231 low, electrically insulative means, the interior of which sur- [51] Int. Cl H011 27/30 rounds a portion f the transformer core means and the exteri [50] Field of Search 336/198, or f which is provided with a plurality f axially spaced 208, 231, 225 cumferential slots. The slots for the high voltage windings are located at progressively increasing radial distances from the [56] References Cited core means portion so as to provide a sufficiently great insula- UNITED STATES PATENTS tive barrier between the coil and the core means to prevent 774,759 11/1904 Kinnaide 336/231X electrical arcing therebetween.

GROU I 48 1 2o 47 49 n L h I l 1 J l 4 BO BZR 37 eef f Patented A ril 6, 1911 GROUPIk GRou H I 48 F'IG.3

HIGH VOLTAGE TRANSFORMER FOR TELEVISION RECEIVERS BACKGROUND OF THE INVENTION This invention relates to high frequency pulse transformers and, more particularly, to an improved transformer of the aforedescribed type which can be used as a horizontal output and high voltage transformer for television receivers and the like.

Heretofore, layer-wound transformers have beenemployed in this service. U. S. Pat. Nos. 2,500,766 and 2,6l2,545 describe typical versions of such conventional transformers. With these prior-art transformers, the tapes and insulating sheets which have been used between the layers of wire forming the coils and the overlapping of the coil layers over one another have retarded the transfer of heat away from the coil to the surrounding atmosphere. Furthermore, it has been difficult to.obtain consistency in operating characteristics with these conventional layer-wound transformers and their production has required a slow and tedious manufacturing process.

SUMMARY OF THE INVENTION To overcome the aforenoted shortcomings of these conventional layer-wound transformers, the present invention has been developed which provides a novel slot-wound transformer that can be used in small and large screen color and monochrome television receivers. Basically, the novel improved transformer of the present invention performs the same operation as the conventional layer-wound transformer which it replaces, differing mostly therefrom in that it employs novel slotted coil form means around which the transformer coils are wound. The novel coil form means comprises hollow electrically insulative means, the interior of which surrounds a portion of the transformer core means and the exterior of which is provided with a plurality of axially spaced circumferential slots. The slots for the high voltage coil windings are located at progressively increasing radial distances from the core means portion so as to provide a sufficiently great insulative barrier between the coil and the core means to prevent electric arcing therebetween. The transformer of the present invention presents improvements over the conventional layerwound transformer, which it replaces, in relation to such factors as more efficient transfer of heat away from the coil windings to the surrounding atmosphere, greater ease and lower costs of manufacture, and increased reproducibility and reliability.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is illustrated in the accompanying drawing, wherein: 1

FIG. 1 is a side elevational view of an assembled transformer incorporating the present invention;

FIG. 2 is a right end elevational perspective view of the transformer illustrated in FIG. I; and

FIG. 3 is an enlarged, somewhat schematic sectional view taken along line 3-3 of FIG. 2, with the U-bolt removed to show details.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing and particularly to FIG. 1 thereof, there is shown a presently preferred form of the improved transformer 10 of the present invention. The transformer I is mounted on a portion of a shielding wall or other suitable support 11 that is provided within the housing of a television receiver or similar device (not shown). A pair of U- shaped sections 12 and 13, which may be molded of a ferrite or other suitable magnetic material, are assembled such that the legs of the U-shaped sections I2 and I3 confront each other. When so assembled, these magnetic sections form generally rectangular core means 14 for the transformer and define a core window 15 at the center of the rectangle.

In order to hold the transformer 10 in its assembled position, a U-bolt 16 is provided. The U-bolt 16 has a pair of legs 17, which are threaded at their distal ends and extend through matching grooves 18 provided in the legs of the core members 12 and 13. The legs of the U-bolt 16 may be passed through apertures provided in the support plate 11 and the entire transformer 10 retained in its assembled position by means of a pair of nuts 19.

In accordance with the present invention, the improved transformer 10 is provided with novel slotted coil form means 20 around which the transformer coils are wound.

Heretofore, the windings for such a transformer have been concentrically wound in layers, one layer directly over another, around an electrically insulative hollow cylindrical coil form that surrounded a portion of the core means. The windings have been arranged on these prior-art cylindrical coil forms with the higher voltage windings located radially farthest from the core and thus having the greatest insulative gap between them and the core in order to inhibit electric arcing between the coil and the core. While this prior-art concentric layer-wound coil construction has served to inhibit electric arcing between the coil and the core, the tapes and insulating sheets which have been used between the layers of wire forming the coils and the overlapping of the coil layers over one another have retarded the transfer of heat away from the coil to the surrounding atmosphere. This problem of retarded heat transfer has, on occasions, resulted in thermal destruction of these prior-art transformers and of the receivers employing them.

In an initial effort to overcome the aforenoted problem of poor heat transfer, it was proposed that the windingsbe axially spaced along the cylindrical coil form such that the winding' surface area exposed to the surrounding atmosphere would be vastly increased and the rate of heat transfer from the coil to the atmosphere would consequently be greatly accelerated. However, these first attempts, while improving heat transfer from the coil, were otherwise unsuccessful in that considerable electric arcing occurred between the high voltage windings and the core when a simple cylindrical coil form was employed.

In accordance with the present invention, it has been found that the novel coil form means 20 provide a solution to the prior-art problem of retarded heat transfer from the trans former coil to the surrounding atmosphere while avoiding any new problem with electric arcing between the coil high voltage windings and the core means 14. In the form of the present invention illustrated in the drawing, the novel coil form means 20 is formed of an electrically insulative material. While various electrically insulative materials may be utilized to produce the novel coil means 20, good results have been obtained with flame-retardant polypropylene material, such as Escon or Avisun 2356. And, although it might also be made of a plurality of parts, the novel coil form means 20 illustrated comprises a lone hollow member, the interior of which surrounds a portion of the core means 14 and the exterior of which is provided with a plurality of axially spaced circumferential slots 29-39 in which the coil windings are wound. As shown, the interior of the novel coil form means 20 comprises a hollow tubular portion 21 that is adapted to be slipped over and to surround the portion of the core means 14 that is defined by the legs of the core members 12 and 13 which comprise the upper wall of the core window 15. The exterior of the novel coil form means 20 comprises a generally frustoconical portion 22 having its convergent end joined to one end of the tubular interior portion 21 of the coil form means 20 and its divergent end being spaced apart from the tubular interior portion 21 by a gap 23 containing air or some other gaseous material. The axially spaced circumferential coil-receiving slots 29-39 are provided in the generally frustoconical exterior portion 22 of the coil form means 20 and are separated from one another by partition members or ribs 40-49.

As best shown in FIG. 3, the slots 29-39 in the exterior of the novel coil form means 20 may be considered as being divided into two groups, Groups I and II. Group I includes two narrow slots 29 and 30 and one wide slot 31. The two narrow slots 29 and 30 receive the transformer auxiliary windings 50 for such auxiliary functions as boost voltage, AFC pulse, AGC keyer pulse, etc. The wide slot 31 receives the transformer primary windings 51. Group II includes the remaining slots 32- -39 which receive the transformer high voltage windings 52. The sizes of the slots 29-39 are of course determined by the size of the wire to be used and the number of turns required. The first three slots 29-3l adjacent the convergent end of the coil form means 20 receive the auxiliary windings 50 and primary windings 51 for the transformer 10. These three slots 29- -31 and at least one slot for the high voltage windings 52 (the slot 32 nearest the primary winding slot 31 as illustrated in the drawing) are spaced at substantially the same radial distance R from the portion of the core means 14 which the coil form means 20 surrounds, while the remaining high voltage winding slots 33-39 are located at progressively increasing radial distances R R R, from that portion of the core means 14 such that a sufficiently great insulative barrier is provided between the transformer coil and the core means to prevent electric arcing therebetween.

By way of example, if R,, R R R, are the radial distances between the successive slots in the high voltage winding Group II from the core means, then:

sary insulative barrier or gap required to prevent arcing between the coil slot sections and the core and distances R and X and Y are the necessary insulative gap or barrier required to prevent electric arcing between the coil and the core at the maximum voltage at which the transformer is to be operated.

As further shown in FIG. 1, each of the partitions or ribs 40- 49 on the exterior of the coil form means is provided with a narrow slit 40s49s to permit continuous winding of the coil-forming wires from slot to slot. While slotted bobbins having slits between their slots to provide for continuous winding are well known, the slits 40s49s which the present inven tion provides are advantageously novel in that they are canted at an angle with respect to the long central axis of the portion of core means 14 that is surrounded by the novel coil form means 20. Thus, with their canted arrangement, the novel slits 40s-49 provide a longer and, thus, greater, electrically insulative barrier to electrical arcing between coil sections located in adjacent ones of the slots 29-39 than has been the case with prior-art slotted coil forms or bobbins wherein such slits have been arranged parallel to the long central axis of the surrounded portion of the core means. Also, the novel canted slits Mix-49s of the present invention prevent bulging of the coil windings in adjacent ones of the slots 29-39 toward one another through the slits; a problem which had existed with the conventional parallel slits.

Still further, in accordance with the present invention, as best shown in FIG. 3, the outer edges of the partitions or ribs 40-49 of the novel coil form means 20 are rounded over. This rounding over of the edges of the partitions or ribs 40 -49 has been found to increase the corona start voltage from coil form means 20 and to thus further insure against electrical arcing. And, by providing the interior of the novel coil form means 20 with the electrically insulative tubular portion 21 shown in the drawing, the surface leakage path between the high voltage windings in the slots at the divergent end of the coil form means 20 and the core means 14 is greatly lengthened. With the coil form means 20 shown, such surface leakage must take the long path defined by the divergent end of the coil form means exterior portion 22, the inner surfaces of the slots 33-39 and the length of the tubular portion 21 of the coil form means 20 that is exposed to the airor gas-filled gap 23.

Thus, from the foregoing, it seems adequately clear that the present invention provides a greatly improved high frequency pulse transformer 10 which can be used as a horizontal output and hi h volta e transformer for television receivers and the like. e nove slotted coil form means 20 employed by the transformer 10 of the present invention permits solution of the longstanding prior-art problem of retarded heat transfer from the coil of conventional transformers used for this service, while avoiding any new problems with electric arcing between the coil high voltage windings 52 and the core means 14. The novel coil form means 20 of the present invention is further advantageous in that it permits continuous winding of the transformer coil windings and consequent reduction in manufacturing costs over the layer-wound coils which have heretofore been utilized for this purpose.

While the herein-illustrated embodiment of the coil form means 20 of the present invention is shown as being provided with the ribs or partitions 4049 on the sides of the windingreceiving slots 2939, it should be understood that these ribs might be omitted, with the exterior portion 22 of the core form means 20 thus presenting a stair-step configuration.

It should be apparent to those skilled in the art that while there has been described what, at present, is considered to be the preferred embodiment of this invention in accordance with the Patent Statutes, changes may be made in the disclosed apparatus without actually departing from the true spirit and scope of this invention.

We claim:

1. An improved high voltage transformer for television receivers and the like, comprising:

a. core means;

b. slotted coil form means comprising hollow electrically insulative means comprising a first and a second portion, said first portion surrounding a portion of said core means and having a substantially constant inside diameter, said second portion being disposed about said first portion and having a progressively increasing inside diameter, said second portion having a plurality of axially spaced circumferential slots formed thereon for receiving high voltage windings; and

c. said circumferential slots being located at progressively increasing radial distances from said core means portion so as to provide a sufficiently great insulative barrier between the coil and the core means to prevent electric arcing therebetween.

2. The invention of claim 1, wherein said high voltage winding slots are spaced apart from said core means portion by a gap of gaseous material.

3. The invention of claim 2, wherein said gaseous material comprises air.

4. The invention of claim 1, wherein:

a. said slots are separated from one another by electrically insulative partitions; and

b. said partitions are provided with slits canted at an angle with respect to the long central axis of said core means portion for permitting continuous coil winding from one slot to another while providing sufficiently great insulative barriers in said partitions to prevent electric arcing between winding sections in adjacent ones of said slots.

5. The invention of claim 4, wherein the edges of said partitions are rounded.

6. The invention of claim 3, further including primary windings disposed in ones of said circumferential slots located at a common, smallest radial distance from said core means, and secondary windings disposed in ones of said winding slots located at progressively increasing radial distances from said core means.

7. The invention of claim 3, wherein said first portion of said coil form means comprises an electrically insulative, generally tubular element, said first portion being joined to said second portion at the smallest diameter end of said second portion. 

1. An improved high voltage transformer for television receivers and the like, comprising: a. core means; b. slotted coil form means comprising hollow electrically insulative means comprising a first and a second portion, said first portion surrounding a portion of said core means and having a substantially constant inside diameter, said second portion being disposed about said first portion and having a progressively increasing inside diameter, said second portion having a plurality of axially spaced circumferential slots formed thereon for receiving high voltage windings; and c. said circumferential slots being located at progressively increasing radial distances from said core means portion so as to provide a sufficIently great insulative barrier between the coil and the core means to prevent electric arcing therebetween.
 2. The invention of claim 1, wherein said high voltage winding slots are spaced apart from said core means portion by a gap of gaseous material.
 3. The invention of claim 2, wherein said gaseous material comprises air.
 4. The invention of claim 1, wherein: a. said slots are separated from one another by electrically insulative partitions; and b. said partitions are provided with slits canted at an angle with respect to the long central axis of said core means portion for permitting continuous coil winding from one slot to another while providing sufficiently great insulative barriers in said partitions to prevent electric arcing between winding sections in adjacent ones of said slots.
 5. The invention of claim 4, wherein the edges of said partitions are rounded.
 6. The invention of claim 3, further including primary windings disposed in ones of said circumferential slots located at a common, smallest radial distance from said core means, and secondary windings disposed in ones of said winding slots located at progressively increasing radial distances from said core means.
 7. The invention of claim 3, wherein said first portion of said coil form means comprises an electrically insulative, generally tubular element, said first portion being joined to said second portion at the smallest diameter end of said second portion. 